1. Technical Field
The present invention relates to a resonator element, a resonator having the resonator element, an oscillator having the resonator element, and an electronic device having the resonator element.
2. Related Art
JP-A-2002-280870 discloses a resonator element which includes a base and a resonating arm portion (hereinafter, referred to as a resonating arm) protruding from the base, and in which a groove is formed in the resonating arm, and a cut-out portion (hereinafter, referred to as a notch) is formed in the base.
In the resonator element disclosed in JP-A-2002-280870, since a notch is formed in the base, a leakage of vibration from the resonating arm to the base decreases. Thus, it is possible to suppress fluctuation of the CI (Crystal Impedance) value (Q value).
The outer shape of the resonator element is generally formed by etching. A resonator element made from a quartz crystal has etching anisotropy: that is, the etching rate differs depending on the direction with respect to the quartz crystal axes of the quartz crystal.
Due to this etching anisotropy, the resonator element at the tip end of the notch in the base is over-etched (excessively etched). Thus, the notch goes further into the central side of the base from an original position. As a result, the notch has a shape, such as a wedge with an acute tip end, such that stress is likely to be concentrated on it.
When an impact, such as by being dropped, is applied to the resonator element, stress is concentrated on the tip end of the notch, and breaking may start from that portion.